Studies in humans by the principal investigator have shown that precipitating serum antibodies to oral bacteria are associated with significant differences in dental caries severity and accumulation of bacterial plaque. One antibody precipitates with an epitope found on macromolecules from Actinomyces spp. and the other with the D-alanyl ester moeity of glycerol teichoic acids from Streptococci and Lactobacilli. Non-precipitating serum antibodies to the polyglycerol phosphate moeity of the latter antigen are not associated with caries severity. The D-alanyl ester epitope is stable at pH 5, but hydrolyses rapidly at physiologic pH. The major specific aim of this study is to quantitate the serum and salivary antibody response to each epitope by a sensitive enzymoimmunoassay in order to examine the relationships between epitope-specific local and systemic antibody responses, age, caries severity and plaque accumulation. A secondary aim is to elucidate a role for genetic constitution in response development. Serum IgG and secretory IgA originate from different modes of antigen exposure and respectively indicate systemic or local immune responses. The respective antigens, in culture filtrates or cell extracts of S. mutans GS-4 and A. viscosus ATCC 19246, will be coated on wells of microplates and the antibody content of serum or salivary samples determined. The amount of antibody bound in the absence or presence of appropriate haptens will be measured with alkaline phosphatase covalently conjugated to goat IgG specific for either human IgG or the secretory chain of human IgA. The difference in binding before and after inhibition will reflect epitope-specific antibody binding and will be quantified by comparison with an appropriate, strongly reactive serum. The relationship of the epitope-specific antibody binding contents to precipitin responses will be examined by multiple discriminant analysis. The interrelationship of the respective antibody contents to each other, age, caries severity, length of fluoride exposure, plaque accumulation and gingivitis will be examined by multiple regression analysis over the whole population and within various serum and saliva antibody response groups. Differences in caries severity or expression of HLA-A, B, C and DR specificities respectively by antibody response group will be examined by multiple discriminant analysis. The findings should identify new factors associated with caries protection and susceptibility.